Researchers using ground-based telescopes have uncovered a planet orbiting its star at a highly unusual angle. The discovery of TOI-3884b's 62-degree tilt relative to the star's rotation challenges current understandings of planetary system formation. No massive companions explain the misalignment, making the system a key target for further study.
A team of astronomers has revealed the peculiar orbital dynamics of TOI-3884b, a planet transiting its host star. Observations captured rare events where the planet passed over cooler starspots, providing insights into the system's geometry.
In February and March 2024, scientists employed the multicolor MuSCAT3 and MuSCAT4 instruments on the Las Cumbres Observatory's 2-meter telescopes. They recorded three transits, detecting signals as the planet crossed dark regions on the star's surface. These starspots are about 200 K cooler than the surrounding 3150 K stellar surface and occupy roughly 15% of the visible area. Subtle variations in the transit shapes over this short period aligned with the star's rotation rather than spot evolution.
To confirm the star's rotational behavior, the researchers conducted photometric monitoring from December 2024 to March 2025 using the Las Cumbres Observatory's global network of 1-meter telescopes. Multiple nightly brightness measurements revealed regular variations, establishing the star's rotation period as 11.05 days.
Integrating these findings, the team determined that the planet's orbital axis is tilted by approximately 62 degrees from the star's spin axis. Such significant misalignments typically arise from gravitational interactions with massive planets or stellar companions, yet none have been detected in this system. This anomaly positions TOI-3884 as a compelling case for investigating planetary system histories.
The results appear in The Astronomical Journal (2025, volume 170, issue 4).